Schlumberger



Feb. 28, 1956 M. SCHLUMBERGER 2,736,260

ELECTRI FIRING SYSTE OR X LOSIVELY ERATED BOREHO TO Filed Nov. 19, 19492 Sheets-Sheet 1 F'IGJ.

v l NTOR. IO MARCEL SC MBERGER H IS ATTORNEYS.

Feb. 28, 1956 M. SCHLUMBERGER 2,736,260

ELECTRICAL FIRING SYSTEM FOR EXPLOSIVELY OPERATED BOREHOLE TOOLS 2Sheets-Sheet 2 Filed Nov. 19, 1949 l m H a l INVENTOR. MARCELSCHLUMBERGEFi $122 f' mm HIS ATTORNEYS.

2,736,260 Patented Feb. 28, 1956 ELECTRICAL FIRING SYSTEM FOREXPLOSIVELY OPERATED BOREHOLE TOOLS Marcel Schlumberger, Paris, France,assignor to Societe de Prospection Electrique Procedes, Schlumberger,Paris, France, a corporation of France Application November 19, 1949,Serial No. 128,386 Claims priority, application France February 19, 19499 Claims. (Cl. 102-20) The present invention relates to firing systemsfor exposive charges and more particularly to new and improvedelectrical systems for setting off a plurality of explosive chargeseither one by one or as a group in predetermined sequence.

In producing oil from wells, explosively propelled projectiles arewidely used in sample taking and casing perforating operations, forexample. The systems currently employed for setting off the explosivecharges in the well from the surface of the earth are relatively complexand tend to be faulty in operation at the excessive temperaturesencountered in the exceedingly deep holes now being drilled. Moreover,bore hole tools of recent design in which the explosive power has beenincreased, are subjected to greater shocks so that the frequency ofoccurrence of faulty operations has gone up.

It is an object of the invention, accordingly, to provide new andimproved firing systems for explosive charges which are free from theabove noted deficiencies of the prior art.

Another object of the invention is'to provide new and improved firingsystems of the above character which are simple and rugged inconstruction yet highly effective in operation.

Still anotherobject of the invention is to provide new and improvedfiring systems of the above character in which the explosive charges maybe fired one by one.

A further object of the invention is to provide new and improved firingsystems of the above character by means of which a group of explosivecharges may be set off substantially simultaneously in predeterminedsequence.

These and other objects of the invention are attained by providing aplurality of igniters of equal resistance for the respective explosivecharges and connecting them in an electrical network simulating atransmission line. More particularly, the igniters are shunted acrossthe line and equal resistances are inserted in series with the line between adjacent igniters, the line being terminated in its characteristicimpedance. For ignition of the entire group of igniters in sequence,constant current is supplied to the network and its intensity isadjusted to the value required just to ignite the first igniter. Underthese conditions, the entire group of igniters will be ignitedsequentially.

In another embodiment, constant current of the proper value just toignite the first igniter is supplied to the network through hold-inswitch means at the surface of the earth and normally closed concussionresponsive switch means in the bore hole. When the hold-in switch meansis closed, it is maintained closed so long as current is flowing to thenetwork. Upon ignition of the first igniter, the shock of the explosionopens the concussion responsive switch means, stopping the flow ofcurrent and opening the hold-in switch means. The concussion responsiveswitch means again closes but the hold-in switch means must again beclosed in order to ignite the next succeeding igniter. With thisconstruction, therefore, the igniters may be ignited one by one, asdesired.

The invention may be better understood from the following detaileddescription of several typical embodiments thereof, taken in conjunctionwith the accompanying drawings, in which:

Fig. 1 is a schematic diagram of an electrical firing circuitconstructed according to the invention for firing a group of explosivecharges in a bore hole tool substantially simultaneously inpredetermined sequence;

Fig. 2 is a view in elevation of gun perforator apparatus embodying thenovel firing circuit shown in Fig. 1;

Fig. 3 is a view in transverse section taken along line 3-3 of Fig. 2;and

Fig. 4 is a schematic diagram of a modified form of firing circuitdesigned to permit the explosive charges in a bore hole tool to be setoif one by one.

While the novel firing systems of the invention are of general utilityfor controlling the firing of a plurality of explosive charges from arelatively remote point, they will be described herein, by way ofexample, as applied to gun perforating apparatus of the type usuallyemployed for perforating a bore hole casing.

- Referring first to Fig. 1, the box 10 designates a gun perforatoradapted to be lowered into a bore hole 11 which usually contains acolumn of conducting liquid 12. As shown in Fig. 2, the perforator 10may comprise, for example, a substantially cylindrical body 13, made ofsteel or other suitable strong material, for example, having a roundedcap 14 at the lower end thereof to facilitate the passage of theapparatus through a well. The upper end of the body 13 is joined by aconventional coupling member 15 to a cable head 16 in which is secured asupporting cable 17, in the usual manner.

Longitudinally spaced along the body 13 and angularly disposed about thelongitudinal axis thereof are a plurality of laterally extending gunbarrels 18. As shown in Fig. 3, each gun barrel 18 is adapted to bescrewed into a threaded bore 19 in the body 13 and it has a flangedportion 20 adapted to be seated in a recess 21, suitable gasket means 22being provided to insure a watertight joint. Recesses 23 or othersuitable means may be formed in the barrel 18 to facilitate itsinsertion and removal by wrench means.

Each of the bores 19 has a substantially cylindrical rear portion 24,and a portion 25 which converges rearwardly to a circular depression 29surrounding a fiat raised portion 27. The bore portions 24 and 25cooperate with a rearwardly converging portion 28 formed on the gunbarrel 18 to form a substantially annular powder chamber 30.

The powder chamber 30 is adapted to receive an explosive charge 31 in acontainer of similar shape which may be made of plastic material, forexample, and which is provided with a flat base portion 32 which isadapted to lie just above the raised portion 27.

In each gun barrel 18 is formed a gun bore 26 which is adapted toreceive a casing perforating projectile 33. The projectile 33 ispreferably provided with a forward stopper member 34 made of flexiblematerial such as rubber, for example, and a rear, burr eliminatingmember 35. Projectiles of this type are disclosed in the copendingapplication Serial No. 120,084, filed October 7, 1949, by Pierre Dubost,for Fluid Scaling and Burr Elimination Projectile for Gun Perforators.

The explosive charge 31 may be ignited by an electrical igniter 36, oneend of which is connected to the pointed end of a conducting tube 37tightly fitted in an adapter 38 threaded into a bore 39 formed in theperforator body 13. igniters of this type are more fully described inthe applicants copending application Serial No. 128,323; filed November19, 1949, for Electrical Igniters. The other end of'the igniter 36 isconnected to a conductor 40 which is insulated from the conducting tube37 and which is connected to a conductor 41. Suitable gasket means 42'and packing means 43 maybe employed to prevent the entrance of bore holefluid through the bore 39.

The conductor 4:1 is disposed in a spiral groove 42. formed in the outerwall of the perforator body 13 and it is connected at its upper andlower ends to the terminal blocks 43 and 4-4, respectively (Fig. 2). Theterminal blocks 43 and 44 and the groove 42 permit easy removal of thewire 41 yet prevent excessive wear of the wire 41 in passing through thebore hole. As a further precaution against wear, a steel strip 60 may beplaced in the groove 42 over the wire 41.

As best shown in Fig. l, the igniters 36 for the several explosivecharges 31 in the gun perforator 10 are connected between the conductor41 and ground. Further, the system is so designed that the resistancesof the pertions 45 of the conductor 41 lying between adjacent igniters36 are equal. The electrical network comprising the shunt igniters 36and the series sections of the conductor 41 simulates an electricaltransmission line.

According to the invention, the network is terminated in a resistance 46which is equal to the characteristic impedance of the line. In a typicalsystem, the resistance values for igniters 36 and the conductor portions45 might be 2 ohms and 1 ohm, respectively, in which case the resistor46 would have a value of 2 ohms, for example.

It will be understood, therefore, that if the current supplied to thenetwork is just enough to insure ignition of the topmost igniter 36, thecurrents flowing through the other igniters 36 will be less than thatrequired for their ignition. Further, upon destruction of the topmostigniter 36 following ignition thereof, the impedance of the networkmeasured at the next succeeding igniter 36 is substantially the same sothat, if current of the same constant intensity is supplied, the currentthrough the next succeeding igniter will be just sufficient for itsignition, while the currents through the remaining igniters will not besuflic'ient for their ignition.

The upper end of the conductor 41 (Fig. 2) is connected to a conductor47 in the supporting cable 17 which may be connected to one terminal ofa suitable source of constant current 43 (Fig. 1) located at the surfaceof the earth, the other terminal of which is grounded at 52. The source48 may comprise, for example, a battery 49 connected in series with aresistance 50 which is relatively large as compared with the totalresistance introduced by the conductor 41.. A conventional switch '51may be interposed between the source 48 and the ground 52 and aconventional current indicating instrument 53 may be inserted in serieswith the conductor 47 so that the current flowing to the network may beobserved.

In operation, the perforating apparatus is lowered into the well withthe switch 51 open, as shown in Fig. 1. When the desired level forperforation has been reached,

the switch 51 is closed, thus supplying to the network current ofconstant intensity and causing ignition of only the first igniter 36.This sets oil the topmost explosive charge 31 and destroys the topmostigniter 36. The transient effect produced by the sudden opening of thecircuit causes a slight deflection on the meter 53. The next igniter 36now receives sufficient current for its ignition while the remainingigniters receive less current than the amount required for ignition sothat the second explosive charge is set otf in the same manner. Insimilar fashion, the remaining explosive charges are exploded insequence. It will be understood that the sequence of events describedabove takes place very rapidly so that the explosive charges in theperforating apparatus are set off substantially simultaneously. Theconstant reading of the meter 53 will indicate to the operator that theoperation is complete so that he can open the switch 51 and withdraw thetool from the bore hole 10.

If it is desired to set ofif the explosive charges 31 one by one, asdesired, the system shown in Fig. 4 may be employed. The firing networkin this figure is essentially the same as shown in Fig. 1 but aconcussion responsive switch 54 is disposed in the bore hole with theperforating apparatus 10, and a hold-in switch 55 is connected in serieswith the conductor 47 at the surface.

The switch 54 is so designed that it normally connects the conductor 41to the cable conductor 47 but when an explosive charge is set off, theconcussion developed operates the switch 54 and breaks the connectionbetween the two conductors. To this end, the switch 54 may comprise, forexample, a switch which is normally maintained closed by a steel ballresting on the switch actuator, the ball being so disposed as to bethrown otf the switch actuator by the concussion developed and to returnto its rest position on the switch actuator after the forces of:concussion have been dissipated.

The switch 55 may be provided with a hold-in coil 56 which is energizedwhen the switch is closed and which holds the switch closed until thecircuit is subsequently opened.

In operation of the embodiment shown in Fig. 4, the perforatingapparatus 10 is moved to the desired level in the bore hole whereuponthe switch 55 is closed. It then remains closed by operation of theholding coil 56. This ignites the first igniter 36 and explodes thefirst explosive charge 31. The concussion developed by the explosionjars the switch 54 causing it to break the energizing circuit and todeenergize the hold-in coil 56 of the switch 55, permitting the latterto open. This operation takes place before the current supplied to thenetwork has had an opportunity to rise to the value required forignition of the next succeeding igniter 36. it will be understood,therefore, that the switch 55 must be actuated each time an igniter 35is to be ignited. Hence, the several igniters 36 can be exploded one byone at different depths in the bore hole, if desired.

Where it is desired to set oif more explosive charges than can beaccommodated in a single perforator body 13, it will be understood thatthe plug 14 may be removed so as to permit additional bodies to beattached to the body 13. In such case, the terminal block 43 of a lowerperforator body 13 will be connected to the terminal block 44 of thenext higher perforator body, and the resistance 46 (Fig. 1) will beconnected from the terminal block 44 of the lowermost perforator body 13to ground.

It will be understood from the foregoing description that the inventionprovides a novel and highly effective firing circuit for controlling thefiring of a plurality of explosive charges from a relatively remotepoint. By connecting the igniters for the explosive charges in a networksimulating a transmission line and terminating the network in thecharacteristic impedance of the line, a group of igniters may be firedin sequence and substantially simultaneously. Further, by incorporatingin the circuit a hold-in switch at the surface together withpercussionresponsive switch means in the bore hole, the igniters may beset off one by one, as desired.

It will be further understood that the specific embodiments disclosedherein are susceptible of considerable modification within the spirit ofthe invention. For example, an alternating current source may beemployed instead of D. C., provided that an equivalent A. C. impedancenetwork is substituted for the resistance network shown in the severalforms of the invention described above. Also, headphones or aloudspeaker might be loosely coupled to the conductor 47 to obtainaudible indications of the operation of the apparatus. The illustrativeembodiments disclosed herein, therefore, are not to be regarded aslimiting in any way the scope of the following claims.

I claim:

1. In a system for controlling the firing of a plurality of explosivecharges, the combination of an electrical transmission channel having aninput end and a terminus, a plurality of electrical igniters of equalimpedance connected in shunt in said channel, a plurality of equalimpedances connected in series in said channel between adjacentigniters, and an impedance connected to said channel at the terminusthereof and being substantially equal to the characteristic impedance ofsaid channel.

2. In a system for controlling the firing of a plurality of explosivecharges, the combination of an electrical transmission channel having aninput end and a terminus, a plurality of electrical igniters of equalimpedance connected in shunt in said channel, a plurality of equalimpedances connected in series in said channel between adjacentigniters, a source of current connected to the input end of saidchannel, switching means interposed between said source and the channel,and an impedance connected to the terminus of said channel, the value ofsaid last named impedance being substantially equal to thecharacteristic impedance of the channel.

3. In a system according to claim 2, the provision of means formaintaining the current from the source of current at a constantamplitude when said switching means connects said source to thetransmission channel.

4. In a system for controlling the firing of a plurality of explosivecharges, the combination of a plurality of electrical igniters, aplurality of impedances, means connecting said igniters in shunt andsaid impedances in series between adjacent igniters to form a simulatedtransmission line, a source of electrical energy connected to one end ofsaid line, manually operable, switching means having current responsivehold-in means interposed between the source and said one end of theline, and normally closed concussion responsive switching meansinterposed between the source and said one end of the line forinterrupting the connection therebetween.

5. In a system for controlling the firing of a plurality of explosivecharges, the combination of a plurality of electrical igniters of equalimpedance, a plurality of equal impedances, means connecting saidigniters in shunt and said impedances in series between adjacentigniters to form a simulated transmission line having an input end and aterminus, a source of electrical energy connected to the input end ofsaid line, hold-in switching means interposed between the source andsaid input end of the line, normally closed concussion responsiveswitching means interposed between the source and said input end of theline, and an impedance connected to said terminus of the line, saidlast-named impedance having a value substantially equal to thecharacteristic impedance of the line.

6. In a system for controlling the firing of a plurality of explosivecharges in a bore hole tool adapted to be lowered into a bore hole, thecombination of a plurality of electricaligniters of equal impedanceassociated with corresponding explosive charges in the tool, a pluralityof equal electrical impedances, means connecting said igniters in shuntand said impedances in series between adjacent igniters to form asimulated electrical transmission line having an input end and aterminus, an impedance connected to the terminus of said line and equalto the characteristic impedance of said line, a source of electricalenergy at the surface of the earth, electrical connections between saidsource and the input end of the line, and switching means interposedbetween the source and said input end of the line.

7. In a system for controlling the firing of a plurality oflongitudinally spaced apart explosive charges in a bore hole tooladapted to be lowered into a bore hole, an electrical conductor carriedby the tool and extending longitudinally thereof, a plurality ofelectrical igniters of equal impedance associated with the explosivecharges in said tool, respectively, the opposite ends of each of saidigniters being connected to ground and to a point on said conductor,respectively, such that the latter introduces equal amounts of impedancebetween adjacent igniters, a source of electrical energy at the surfaceof the earth having a terminal connected to one end of said conductorand another terminal connected to ground, switching means interposedbetween the sourceand said one end of the conductor, and an electricalimpedance connected to the other end of said conductor and to ground andequal in value to the characteristic impedance of the simulatedtransmission line formed by said igniters and conductor.

8. In a system for controlling the firing of a plurality of explosivecharges in a bore hole tool adapted to be lowered into a bore hole, thecombination of a plurality of electrical igniters of equal impedanceassociated with corresponding explosive charges in the tool, a pluralityof equal electrical impedances, means connecting said igniters in shuntand said impedances in series between adjacent igniters to form asimulated electrical transmission line having an input end and aterminus, an impedance connected to said terminus of said line and equalto the characteristic impedance of said line, a source of electricalenergy at the surface of the earth, electrical connections between saidsource and the input end of the line, normally open switching means atthe surface of the earth for controlling the connections between thesource and said input end of the line, means responsive to currentflowing to said line for maintaining said switching means closed, andnormally closed concussion operated switching means operativelyassociated with said tool for breaking the connections between thesource and said input end of the line to render said current responsivemeans inoperative.

9. In a system for controlling the firing of a plurality oflongitudinally spaced apart explosive charges in a bore hole tooladapted to be lowered into a bore hole, an electrical conductor carriedby the tool and extending longitudinally thereof, a plurality ofelectrical igniters of equal impedance associated with the explosivecharges in said tool, respectively, the opposite ends of each of saidigniters being connected to ground and to a point on said conductor,respectively, such that the latter introduces equal amounts of impedancebetween adjacent igniters, a source of electrical energy at the surfaceof the earth having a terminal connected to one end of said conductorand another terminal connected to ground, normally open switching meansinterposed between the source and said one end of the conductor, meansresponsive to the current flowing to said conductor for maintaining saidswitching means closed, concussion responsive switching meansoperatively associated with said bore hole tool for breaking theconnections between the source and said one end of the conductor torender said current responsive means inoperative, and an electricalimpedance connected to the other end of said conductor and to ground andequal in value to the characteristic impedance of the simulatedtransmission line formed by said igniters and conductor.

References Cited in the file of this patent UNITED STATES PATENTS1,078,463 Rawson Nov. 11, 1913 1,448,976 Palmer Mar. 10, 1923 2,296,318Thompson Sept. 22, 1942 2,363,234 Doll Nov. 2, 1944 2,369,238 KavelerFeb. 13, 1945 2,381,081 Schlumberger Aug. 7, 1945 2,400,549 Glennon etal May 21, 1946 FOREIGN PATENTS 326,332 France May 23, 1903 757,734France Dec. 30, 1933

